In a photovoltaic system, a part of the sun radiation is converted into electric energy in the form of direct current by means of solar cells. The energy conversion is based on the radiation being subject to an absorption in a solar cell, thus generating positive and negative charge carriers (“electron-hole pairs”). The generated free charge carriers are furthermore separated from each other and are discharged via separate contacts. In a solar module, a plurality of solar cells operating according to this functional principle is generally combined. A photovoltaic system may comprise a plurality of such solar modules, with the solar modules being typically connected in series to form a “string”.
A problem of conventional photovoltaic systems is the possible occurrence of an electric arc. Such an electric arc may be formed over a separation distance if an electrical connection or, respectively, a current flow is interrupted. An electric arc may e.g. occur at a solar module, for example due to a fracture in the region of a cell connector provided for connecting solar cells. Other defective positions are possible, as well, e.g. at a connecting box of a solar module or in the region of a wiring of a photovoltaic system.
Since upon the incidence of light, a photovoltaic system generates direct current which flows through the photovoltaic system and its components, an electric arc may persist for a relatively long duration of time. An electric arc exists as long as current and voltage are sufficiently high in order to maintain the current flow across the separation distance. However, the persistence of an electric arc over a long time may cause considerable material damage and bodily injury (e.g. a fire in a family home).
Conventional approaches for preventing this problem relate to the detection of an electric arc and to the active shut-down in such a case. In this context, e.g. WO 95/25374 A1 describes the detecting of an electric arc by means of the electromagnetic radiation emanating from the electric arc and triggering an alarm on the basis thereof as well as switching a partial region of the photovoltaic system in which the electric arc is located in such a way that the electric arc disappears. However, such a procedure involves high complexity.